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The vibroacoustic level has become a key factor for evaluating permanent magnet motor performance in recent years. However, the influence of tangential force is usually ignored, which will lead to errors in vibration noise calculation and limit the idea of reducing motor vibration noise. In this article, a comprehensive investigation of the tangential - and radial forces and their effects on the motor vibration is conducted. First, the analytical method of the electromagnetic force is presented. Next, the finite element method is applied to analyze the electromagnetic laws of radial force and tangential force. Then, the Theorem of Translation of A Force (TTF) is introduced to describe the influence of tangential force on radial vibration. After that, the influencing factors of stator teeth and load on the radial- and tangential-force are discussed, especially the phase relationship. Finally, the electromagnetic vibration law caused by radial force and tangential force is simulated and verified by experiments. The results can provide guidance for design of low vibroacoustic motor considering radial force and tangential force.

Continuous mode changes during battery charging present a significant challenge for the application of inductive power transfer (IPT) in battery charging. Achieving constant-current (CC) and constant-voltage (CV) charging characteristics is crucial for its successful implementation. This paper proposes a variable static S-T/FC compensation topology based on switching state changes. It offers the advantages of being able to handle various load conditions, facilitating soft switching of the inverter throughout the operation process, and achieving CC and CV charging without changing the operating frequency of the system. The characteristics of the proposed topology were confirmed through a theoretical analysis. Additionally, a completely new parameter design method is proposed. The CC and CV characteristics of the proposed topology are verified through theoretical derivation and simulation analysis. Finally, a validation prototype is constructed to assess the feasibility and rationality of the proposed method, achieving a 3.5 A output current in the CC mode and a 70 V output voltage in the CV mode.

In traditional analysis, several studies have discussed the vibration behavior of electric machines from the point of view of radial force. With the increasingly strict vibroacoustic index, the tangential force effects on the vibration are analyzed and investigated, and it shows the contribution of tangential force on electromagnetic vibration cannot be ignored. However, these studies are based mainly on finite element multi-physics models, and experiments are not conducted. Furthermore, the mechanism of tangential force is not clearly explained. In this paper, a special motor stator structure is proposed to explore the effect of tangential force on vibration. First, the analytical calculation of the tangential force and the tangential effect on motor vibration are described. Next, the Theorem of Translation of A Force is introduced to convert the effective tangential tooth force to a radial force couple acting on the stator yoke. Then, a novel motor stator is proposed to investigate the vibration characteristics caused only by tangential force, and the simulation is analyzed. Finally, a vibration test of the prototype is conducted and the result shows the tangential force can induce the radial vibration with corresponding order.